1. Field of the Invention
The present invention relates to an organic electroluminescence display device, and more particularly to an organic electroluminescence display device that is adaptive for solving an electric contacting defect problem caused between a light emission array and a TFT array, and a fabricating method thereof.
2. Description of the Related Art
Recently, various flat panel display devices have been developed to reduce the weight and size so as to replace a relatively heavy and large-size cathode ray tube. The flat panel display device includes liquid crystal display (LCD), field emission display (FED), plasma display panel (PDP), electro-luminescence (EL) display device and so on.
The PDP has a relatively simple structure and fabrication process. Therefore, the PDP is most advantageous to be made large-sized, but it has a disadvantage in that its light emission efficiency and brightness are low and its power consumption is high. The manufacturing process for the LCD is similar to the semiconductor process. Therefore, the LCD is difficult to be made large-sized, and its power consumption is high due to a backlight unit. Further, the LCD has a disadvantage in that its viewing angle is narrow and there is a high light loss by optical devices such as a polarizing filter, a prism sheet, a diffusion plate and so on. In comparison, the EL display device has an advantage in that its response speed is fast, its light emission efficiency and brightness are high and its viewing angle is wide.
The EL display device is generally divided into an inorganic EL display device and an organic EL display device in accordance with the used material.
The organic EL display device is driven with a low voltage of about 5˜20[V] in comparison with the inorganic EL display device which requires a high voltage of 100˜200[V]. Therefore, it is possible to drive the organic EL display device with a low DC voltage. Further, the organic EL display device can be used as a pixel of a surface light source, a television image display or a graphic display because the organic EL display device has an excellent characteristic such as a wide viewing angle, a high speed response, a high contrast ratio and so on. In addition, the organic EL display has a good color impression and is thin and light. It is a suitable device for the next generation flat panel display.
A method of driving the organic EL display device can be divided into a passive matrix type and an active matrix type.
The passive matrix type organic EL display device is simple in its configuration so its fabricating method is also simple. However, there is a disadvantage in that its power consumption is high, it is difficult to make a display device large-sized, and its aperture ratio is deteriorated as the number of wire lines increases.
On the other hand, the active matrix type organic EL display device has advantages of high light emission efficiency and high picture quality realization.
Further, the organic EL display device can be divided into the Top Emission Type and the Bottom Emission Type in accordance with its light emitting direction.
FIG. 1 is a diagram illustrating an example of the Top Emission Type active matrix organic EL display device in the related art.
Referring to FIG. 1, the Top Emission Type active matrix organic El display device of the related art includes a light emission array 30 comprising a light emitting part formed on a first substrate 1; a TFT array 40 comprising a thin film transistor TFT controlling the light emitting part on a second substrate 2; and a contact part 50 electrically connecting the light emission array 30 and the TFT array 40. Further, the first and second substrates 1, 2 are bonded together by a sealant 60.
The light emission array 30 includes a color filter array, a first electrode 11, an organic light emitting layer 15 and a second electrode 17 which are sequentially deposited on the first substrate 1. Further it includes a barrier rib 13 which separates the organic light emitting layer 15 and the second electrode 17 so as to be form the pixel area.
The color filter array includes a black matrix 3 which prevents light leakage from a pixel and blocks an external light so as to increase contrast ratio; a color filter 5 for realizing color; an auxiliary color layer (or CCM (color change method) layer) 7 for increasing a color reproduction effect of the color filter 5; and an overcoat layer 9 for leveling the color filter array.
The organic light emitting layer 15 includes a hole injecting/transporting layer 15A, a light emitting layer 15B and an electron injecting/transporting layer 15C.
If a voltage is applied between the first electrode 11 and the second electrode 17, a hole generated from the first electrode moves toward the light emitting layer 15B through the hole injecting/transporting layer 15A. Further, an electron generated from the second electrode 17 moves toward the light emitting layer 15B through the electron injecting/transporting layer 15C. Accordingly, the hole and electron collide with each other in the light emitting layer 15B to be re-combined, thereby emitting the light. And, the light is emitted to the outside through the color filter array so that a picture is displayed.
The TFT array 40 includes a semiconductor layer 4, a gate insulating film 6, a gate electrode 8, an interlayer insulating film 10, source and drain electrodes 12, 16, a passivation film 20, and a pixel electrode 22 which are sequentially deposited on the second substrate 2.
As having the injected n+ impurities, the semiconductor layer 4 includes a source area, a drain area and a channel area formed between the source area and the drain area. The semiconductor layer 4 properly further includes an LDD (lightly doped drain) area, where n-impurities are injected, between the channel area and the source and drain areas for reducing an off-current.
The gate electrode 8 is formed to overlap the channel area of the semiconductor layer 4 with the gate insulating film 6. The source and drain electrodes 12, 16 are formed to be insulated with the gate electrode 8 by the interlayer insulating film 10 therebetween. The source and drain electrodes 12, 16 are respectively connected to the source and drain areas of the semiconductor layer 4 through a source contact hole 14 and a drain contact hole 18 which penetrate the gate insulating film 6 and the interlayer insulating film 10.
The pixel electrode 22 is connected to the drain electrode 16 through the pixel contact hole 24 which penetrates the passivation film 20.
The light emission array 30 and the TFT array 40 are electrically contacted with each other through a contact part 50. The contact part 50 includes a contact supporting part 52 and a contact electrode 54. The contact supporting part 52 is formed of a photo-resist pattern. The contact electrode 54 is formed by a mask process to cover the pixel electrode 22 and the contact supporting part 52, and is contacted with the second electrode 17 of the light emission array 30 when bonding the first and second substrates 1, 2, thereby electrically connecting the light emission array 30 and the TFT array 40.
The contact electrode 54 is comprised of a metal material such as aluminum (Al), molybdenum (Mo), chrome (Cr) and so on. In addition, the second electrode 17 of the emission array 30 is also comprised of the metal material. Therefore, the contacting adhesion between the contact electrode 54 and the second electrode 17 is weak. Therefore, it may cause an electric contacting problem that a signal from the TFT array 40 is not properly supplied to the second electrode 17. Further, in case that the photo-resist pattern is not formed in a uniform thickness when forming the contact supporting part 52, the contacting defect problem might be generated because the contact electrode 54 formed on the contact supporting part 52 is thin and may not be in contact with the second electrode 17 of the light emission array 30. Because the contact supporting part 52, the contact electrode 54 and the second electrode 17 are all rigid material such as metal, when joining the contact electrode 54 and the second electrode 17, it is hard to completely contact the second electrodes 17 with the contact electrodes 54 over the entire substrate area. Because it is hard to form the all contact supporting part 52 and the contact electrode 54 to have the exactly same height, a gap may be generated between some contact electrodes 54 and the corresponding second electrodes 17, which causes the contact defect.